1. Field of the Invention.
The present invention relates to a pre-cast panel lifting insert used in combination with a lifting apparatus and a pre-cast panel, whereby the pre-cast panels may be lifted and moved from one place to another with virtually no damage from the stress of lifting. The pre-cast panels may be of any reasonable shape or size and are intended for any number of uses.
2. Description of the Prior Art.
Pre-cast panels are manufactured at a pre-cast fabrication plant or on the construction site. After curing, the panels must be lifted from the forms for shipment or for attachment to the building or other structure under construction. These panels are normally formed with their largest areas oriented in the horizontal position and are usually thin to reduce weight. Improper lifting of these panels results in cracking and failure. This is particularly true if the panels are the sandwich type; that is, comprised of a layer of insulation sandwiched between two layers of concrete. Currently, fastening devices are embedded near the surface of the top layer during the pouring process. Failure frequently occurs when the lifting insert is pulled from the surface or when the unsupported second and third layers separate from the first layer.
A device that is placed within retaining wall panels is disclosed by U.S. Pat. No. 4,449,857 that was issued to Davis. This device is used for attaching deadmen to a retaining wall panel, and may be also used during the lifting and placement process of these panels. This type of device does not distribute the load throughout the panel, which may result in failure, particularly when used with thin panels or sandwich panels.
It is clear that a device is needed to distribute the lifting load throughout the panel, particularly when the device is used with sandwich panels where it is necessary to distribute the load over the bottom layer of a panel to prevent separation of the layers.